2018-11-19T22:43:31ZThe effects of ultrasound parameters and microbubble concentration on acoustic particle palpationhttp://hdl.handle.net/20.500.11779/211
The effects of ultrasound parameters and microbubble concentration on acoustic particle palpation
Saharkhiz, Niloufar; Körük, Hasan; Choi, James J.
The elasticity of tissue—an indicator of disease progression—can be imaged by ultrasound elasticity imaging technologies. An acoustic particle palpation (APP) has recently been developed—the use of ultrasonically driven acoustic particles (e.g., microbubbles)—as an alternative method of tissue deformation. APP has the potential to improve the resolution, contrast, and depth of ultrasound elasticity imaging; but the tissue displacement dynamics and its dependence on acoustic pressure, center frequency, and microbubble concentration remains unknown. Here, displacements of at least 1 μm were produced by applying ultrasound onto a microbubble solution (concentration: 10 × 106 microbubbles ml–1) placed within a tunnel surrounded by a 5% gelatin phantom. Displacements of more than 10 μm were produced using a 1, 3.5, or 5 MHz center frequency pulse with peak-rarefactional pressures of 470, 785, and 1210 kPa, respectively. The deformation of the distal wall varied spatially and temporally according to the different parameters investigated. At low pressures, the deformation increased over several milliseconds until it was held at a nearly constant value. At high pressures, a large deformation occurred within a millisecond followed by a sharp decrease and long stabilization. Ultrasound exposure in the presence of microbubbles produced tissue deformation (p < 0.05) while without microbubbles, no deformation was observed.
2018-08-17T00:00:00ZDetection of air leakage into vacuum packages using acoustic measurements and estimation of defect sizehttp://hdl.handle.net/20.500.11779/203
Detection of air leakage into vacuum packages using acoustic measurements and estimation of defect size
Körük, Hasan; Şanlıtürk, Kenan Yüce
Air leakages in food and ingredient packages which are sealed in vacuum environments may cause a marked deterioration of the product, leading to a loss of functionality. Manufacturers of such products have very stringent but rather costly quality control procedures and there is a pressing need for developing more economical ways of automated quality control techniques to test the vacuum packages reliably. However, due to the fact that the defect size of a typical package with a leakage problem could be micro- or nano-scale, such faults are not detectable using conventional techniques. In this paper, the performance of a proposed acoustic method is assessed for the detection of air leakage in instant dry yeast packages sealed in a vacuum environment, which are typical of food and ingredients packaged under vacuum conditions. The investigation is carried out in both laboratory and in-situ environments. The acoustic pressure created by leaking air into the faulty packages is measured using a low-noise microphone in an acoustic chamber. Faulty packages are then identified using the changes in measured sound pressure levels within a certain frequency band. A mathematical model is also proposed to predict the pressure inside a yeast package with certain defect size as a function of time. The mathematical model is then used to determine the size of a defect causing the leakage, using the time required for the pressure inside a faulty yeast package to reach to a threshold level. The results of this investigation show that, using the state of the art measurement techniques, it is possible to detect packages with leakage problem if the diameter of the defect is greater than a few tens of micrometres.
2019-01-01T00:00:00ZLessons from the rector of the first fully flipped learning universityhttp://hdl.handle.net/20.500.11779/202
Lessons from the rector of the first fully flipped learning university
Şahin, Muhammed
Sahin: MEF Educational Institutions was founded in the 1970s by İbrahim Arıkan, an educator and businessman. In 1996, he founded MEF national and international K-12 schools in Istanbul and Izmir. In 2013, he founded MEF University. As both educator and entrepreneur, Arıkan was in a unique position to establish a university. He was aware the educational system was not well suited to the current needs of students and society and envisioned a totally new educational approach for MEF University. To find this approach, he brought me on board as founding rector. Having been rector of Istanbul Technical University from 2008 to 2012, I had a strong background in innovations in education. During our first meeting, Arıkan made it clear that if he was going to establish a university, it needed to be unique and take a different mentality to the educational needs of today’s students. I vividly remember Ibrahim emphatically declaring that if he could not make a change to higher education, he would call a halt to his aspirations for opening a university.
Dünya Flipped Learning Girişimi’nin yeni eğitim-öğretim yöntemleri ve teknolojileri hakkında dünyada öncülük yapma amacıyla yayınlanan Flipped Learning 3.0 Dergisi’ne MEF Üniversitesi Rektörü Prof. Dr. Muhammed Şahin kapak oldu.
2018-05-08T00:00:00ZInvestigation of the vibro-acoustic behaviors of luffa bio composites and assessment of their use for practical applicationshttp://hdl.handle.net/20.500.11779/201
Investigation of the vibro-acoustic behaviors of luffa bio composites and assessment of their use for practical applications
Genç, Garip; Körük, Hasan
New materials as alternatives to petroleum-based composite materials are needed due to adverse effects of chemical materials on nature. On the other hand, there is a need to characterize and evaluate new alternative materials to be effectively used in practical applications. The vibro-acoustic behaviors including damping and elastic properties, sound absorption and transmission loss levels of luffa bio-composites are investigated and their use for practical applications is evaluated in this study. First, the procedure for manufacturing luffa composites is summarized and materials and methods are presented. After that, the acoustic absorption and transmission loss levels of sample luffa composites are explored by using the impedance tube method. The damping and elastic properties of sample luffa composites are determined by using experimental and theoretical modal data. Furthermore, the interface properties of the luffa fibers and matrix are examined by using Scanning Electron Microscope. All the results are evaluated and the potential of the use of luffa composites in practical applications is assessed.
2016-07-10T00:00:00Z